Aspects of the present disclosure relate to apparatuses, devices, and methods involving integrated capacitors. Such capacitors are suited for use in automotive applications, including automotive isolator devices, which are components that allow the safe transmission of electrical signals between different voltage domains.
More specifically, many automotive applications for electric and hybrid vehicles (electrically driven vehicles) require a high-voltage signal isolator, which can be integrated on a chip. The isolator can be of either single chip or multi-chip design. This invention is directed to an easy to integrate high-voltage capacitor suitable for use in such automotive isolator applications. This invention is not intended to be limited just to such applications, however, and can be employed anywhere there is electrical signaling across different voltage domains, such as in marine and aviation applications.
For example, signal circuits may be galvanically isolated from one another using capacitive coupling on signal paths between the circuits. As a result of such isolation, the circuits operate in separate voltage domains that are not referenced to one another by a common ground voltage level. Consequently, large voltage differences may arise between the different voltage domains. Galvanic isolation has been used for signaling between such different voltage domains in a variety of different applications. For instance, galvanic isolation can be provided between multiple integrated circuit chips, which can be located within the same package or in different packages. Signals can be passed between the integrated circuits using galvanic isolation techniques.
One method of galvanic isolation uses capacitors in the signal paths between two circuits to block DC voltages and attenuate low-frequency signals while transmitting high-frequency signals. Such capacitors can be part of the integrated circuit, as elements formed by the Metal1 to Metal5 (or Metal 6) layers of the integrated circuit fabrication process. However, since large voltage differences may arise between isolated voltage domains for some applications, possibly on the order of several kilovolts for transients, capacitors are required that have higher breakdown voltages than can be achieved using this manufacturing technique.
Also, physical space constraints may make it difficult to implement capacitors having the required breakdown voltage in the fabricated integrated circuits.
For example, a parallel plate capacitor may be implemented alongside other circuitry in an integrated circuit (IC) made using conventional processes for fabricating ICs with multiple internal metal layers (e.g., CMOS). Two capacitor plates are implemented in different metallization layers of the IC and are separated by a dielectric layer. The breakdown voltage of the resulting parallel plate capacitor is in part dependent upon the thickness of the dielectric layer. For higher voltage applications, the thickness of the dielectric layer can be increased to provide a higher breakdown voltage. However, in some CMOS processes, the maximum dielectric thickness that can be achieved is limited to about 5-10 microns. For some applications, this thickness is not adequate to provide a capacitor possessing the breakdown voltage required to insure satisfactory operation.